A panel in a liquid crystal display comprises an array substrate and a color film substrate which are arranged in parallel and opposite one another, between which a liquid crystal layer is arranged. In order to realize a steady thickness of the liquid crystal layer, a spacer is arranged between the two substrates. Currently, a high-performance thin film transistor liquid crystal display (TFT-LCD) panel generally uses a post spacer (PS).
During the fabricating process of the existing thin film transistor liquid crystal display panel, the top face of the post spacer has a convex shape. Under the action of an external force, the top face of the post spacer has a relatively small contact area, while the post spacer itself is elastic and has a relatively large deformation capacity. In addition, with the change in the contact area, the post spacer exhibits a nonlinear variation in its hardness. These properties of the post spacer result in defects in the liquid crystal panel which is sensitive to variation in external pressure. For example, when the liquid crystal panel is in the grayscale L0 black state, the liquid crystal panel may suffer from light leakage (i.e., L0 light leakage). The liquid crystal panel may also suffer from Touch Mura. These defects seriously degrade the display quality of the liquid crystal panel.
In general, the post spacer has a convex top face because of the conventional method for fabricating the post spacer. In the conventional fabricating method, firstly, negative photoresist, which will develop into insoluble material if irradiated by light, is coated on a color film substrate. Then, the negative photoresist is exposed and developed by using a mask plate, in which a portion of the negative photoresist which has been irradiated by light is dissolved and removed, while the negative photoresist under the exposure region of the mask plate becomes insoluble and forms a post spacer. However, in the conventional mask plate, the intensity of light that is transmitted through the exposure region is not uniform, but instead decreases gradually from a center region to an edge region. As a result, the center region of the negative photoresist under the exposure region is irradiated by light with higher intensity and the edge region is irradiated by light with lower intensity, so that upon developing, the negative photoresist in the edge region will be dissolved to a larger extent. In this way, the resultant post spacer has a convex top face.